PL700 Rebuild
- Thread starter Overundr1
- Start date
I haven't seen a 700 in ages (90's I think). After studying the photos and reviewing the manual, the 700 used 2 sets of input jacks (direct and capacitor coupled). The 700B?700II used one set of input jacks and a micro switch to short out the cap for direct coupled.
If I was doing this I would go with 700II config (see attached, page 11) with capacitor coupled and eliminate the switch and 2nd set of jacks. Plan B would use the microswitch to short out the input coupling cap. My logic? Direct coupled amplifies any DC offset of the preamp.
If I was doing this I would go with 700II config (see attached, page 11) with capacitor coupled and eliminate the switch and 2nd set of jacks. Plan B would use the microswitch to short out the input coupling cap. My logic? Direct coupled amplifies any DC offset of the preamp.
Like this without the switch (snipped from the schematic)?
Have not yet received the boards etc from Joe so cannot study them to see if there are coupling caps on the input lines. My usual go to for coupling caps is a 1uf MUSE with a paralleled 0.47 ecq which would be easy enough to either direct wire to the input jacks or at the board input connection point. Interesting side note, a friend is finishing up a very lengthy and thorough restoration and upgrade of a Dynaco ST-400 and we are in a discussion at the moment on how to quell the Frankenstein light dimming that occurs when those twin 15,000uf caps first charge up. Sort of settling on a SL32 inrush limiter thus using him as a test subject for the PL-700 with the same size caps.
Have not yet received the boards etc from Joe so cannot study them to see if there are coupling caps on the input lines. My usual go to for coupling caps is a 1uf MUSE with a paralleled 0.47 ecq which would be easy enough to either direct wire to the input jacks or at the board input connection point. Interesting side note, a friend is finishing up a very lengthy and thorough restoration and upgrade of a Dynaco ST-400 and we are in a discussion at the moment on how to quell the Frankenstein light dimming that occurs when those twin 15,000uf caps first charge up. Sort of settling on a SL32 inrush limiter thus using him as a test subject for the PL-700 with the same size caps.
If I understand the forum consensus - - - Direct wire the rca jacks (one set), eliminate the volume potentiometers (leave them in the front panel for show), trim the copper plate to fit and block off the bottom two and round switch hole with plugs for appearance. Correct?
The new pats including MJ21196G's arrived yesterday, other goodies inbound as well. Project starting to come together.
The new pats including MJ21196G's arrived yesterday, other goodies inbound as well. Project starting to come together.
Wish I could make my solder points as nice as yours sir. Anyways mounted the new rca jacks to the copper board this morning and verified integrity and proper grounding. After deliberation also mounted the bottom two jacks as well. they are 'dummies' at the moment however don't bother anything and keep the back panel looking nos.
Pulled the pre driver caps off the backplane board, they were well beyond their useful life. Supposed to be 4uf.
And installed the new Panasonic 4.7uf 250v ecq's, a snug fit but still clears the control board.
Pulled the pre driver caps off the backplane board, they were well beyond their useful life. Supposed to be 4uf.
And installed the new Panasonic 4.7uf 250v ecq's, a snug fit but still clears the control board.
Yes, ground tabs directly soldered to copper plane, attenuators removed. Like the LED idea, do you remember what size led you ordered?
New binding posts installed.
And Don's most superior speaker relay board mounted. White wires just floating above board not hooked up.
And thats about all I can accomplish until the WOPL order arrives.
Also have black silicone plugs en route for those extra holes drilled in the side panel.
New binding posts installed.
And Don's most superior speaker relay board mounted. White wires just floating above board not hooked up.
And thats about all I can accomplish until the WOPL order arrives.
Also have black silicone plugs en route for those extra holes drilled in the side panel.
Here's the idea and part#'s I used.
My amps are Series 2 with Joe's awesome Meter Boards.
https://forums.phxaudiotape.com/threads/leds-in-place-of-attenuators.10756/
My amps are Series 2 with Joe's awesome Meter Boards.
https://forums.phxaudiotape.com/threads/leds-in-place-of-attenuators.10756/
Busy reading threads as I wait for parts. Seems to be different thoughts on the predrivers. This amp had rca410's on each of the left channel output bank and motorola 7439's on the right channel banks. Question then becomes use one rca in position 2 and 4 counting from the transformer or use the rca in each of the 4 bottom positions as I found it?
Since not much else to do started playing with various led ideas blatantly copying where other members have gone before
Plus it lets me fool around with my bench top power supply, various banana leads of destruction and multiple sizes of rubbers.
After all I am sure I read somewheres in the forum rules we must practice safe mounting of any LED's.
Since not much else to do started playing with various led ideas blatantly copying where other members have gone before
Plus it lets me fool around with my bench top power supply, various banana leads of destruction and multiple sizes of rubbers.
After all I am sure I read somewheres in the forum rules we must practice safe mounting of any LED's.
Busy reading threads as I wait for parts. Seems to be different thoughts on the predrivers. This amp had rca410's on each of the left channel output bank and motorola 7439's on the right channel banks. Question then becomes use one rca in position 2 and 4 counting from the transformer or use the rca in each of the 4 bottom positions as I found it?
Since not much else to do started playing with various led ideas blatantly copying where other members have gone before
Plus it lets me fool around with my bench top power supply, various banana leads of destruction and multiple sizes of rubbers.
After all I am sure I read somewheres in the forum rules we must practice safe mounting of any LED's.
View attachment 83952
Since not much else to do started playing with various led ideas blatantly copying where other members have gone before
Plus it lets me fool around with my bench top power supply, various banana leads of destruction and multiple sizes of rubbers.
After all I am sure I read somewheres in the forum rules we must practice safe mounting of any LED's.
View attachment 83952